A two-fer in terms of items prohibited by Customs...but admittedly beautiful.

From cbp.gov: "You may import an object made of ivory if it is an antique. To be an antique the ivory must be at least 100 years old. You will need documentation that authenticates the age of the ivory. You may import other antiques containing wildlife parts with the same condition, but they must be accompanied by documentation proving they are at least 100 years old. Certain other requirements for antiques may apply."

From cbp.gov: "You may import an object made of ivory if it is an antique. To be an antique the ivory must be at least 100 years old. You will need documentation that authenticates the age of the ivory. You may import other antiques containing wildlife parts with the same condition, but they must be accompanied by documentation proving they are at least 100 years old. Certain other requirements for antiques may apply."